Secondary batteries such as lithium secondary batteries and nickel-hydrogen batteries are used as on-board power sources in electricity-powered vehicles, or as power sources installed in personal computers, handheld devices and other electrical products. In particular, nonaqueous electrolyte secondary batteries, typically lithium secondary batteries that are lightweight and able to achieve a high energy density, are suitable as high-output power sources for on-board use in vehicles such as electric vehicles and hybrid vehicles. Attempts have been made to optimize the compositions of, e.g., the positive and negative electrode active materials and the nonaqueous electrolyte solution in order to achieve the desired power generating characteristics in such nonaqueous electrolyte secondary batteries (see Patent Literature 1 and 2). In addition, the use of a positive electrode active material having a working potential higher than 4.3 V versus metallic lithium has been proposed as a way of further enhancing the high-energy density characteristics in nonaqueous electrolyte secondary batteries.